 Euclid

/yooh"klid/, n.1. fl. c300 B.C., Greek geometrician and educator at Alexandria.2. a city in NE Ohio, near Cleveland. 59,999.
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flourished с 300 BC, Alexandria, EgyptGreek mathematician of antiquity, known primarily for his highly influential treatise on geometry, the Elements.He founded a school in Alexandria during the reign of Ptolemy I. Little is known of his life, but there are many anecdotes. In the most famous, asked by Ptolemy if there is a shorter way to geometry than through his Elements, Euclid replies, "There is no royal road to geometry." The Elements, based on the works of earlier mathematicians, is a brilliant synthesis of old and new. It has been a major influence on rational thought and a model for many philosophical treatises, and it has set a standard for logical thinking and methods of proof in the sciences. The starting point not just of Euclidean geometry but of an approach to reasoning, it is sometimes said to be the most translated, published, and studied work after the Bible.* * *
▪ Greek mathematicianIntroductionGreek Eukleidesborn c. 300 BC, Alexandria, Egyptthe most prominent mathematician of GrecoRoman antiquity, best known for his treatise on geometry, the Elements.LifeOf Euclid's life nothing is known except what the Greek philosopher Proclus (c. AD 410–485) reports in his “summary” of famous Greek mathematicians. According to him, Euclid taught at Alexandria in the time of Ptolemy I Soter, who reigned over Egypt from 323 to 285 BC. Medieval translators and editors often confused him with the philosopher Eukleides of Megara, a contemporary of Plato about a century before, and therefore called him Megarensis. Proclus supported his date for Euclid by writing “Ptolemy once asked Euclid if there was not a shorter road to geometry than through the Elements, and Euclid replied that there was no royal road to geometry.” Today few historians challenge the consensus that Euclid was older than Archimedes (c. 290/280–212/211 BC).Sources and contents of the ElementsEuclid compiled his Elements from a number of works of earlier men. Among these are Hippocrates of Chios (flourished c. 460 BC), not to be confused with the physician Hippocrates of Cos (Hippocrates) (c. 460–377 BC). The latest compiler before Euclid was Theudius, whose textbook was used in the Academy and was probably the one used by Aristotle (384–322 BC). The older elements were at once superseded by Euclid's and then forgotten. For his subject matter Euclid doubtless drew upon all his predecessors, but it is clear that the whole design of his work was his own, culminating in the construction of the five regular solids, now known as the Platonic solids (Platonic solid).Euclid's axioms and common notionsA brief survey of the Elements belies a common belief that it concerns only geometry. This misconception may be caused by reading no further than Books I through IV, which cover elementary plane geometry. Euclid understood that building a logical and rigorous geometry (and mathematics) depends on the foundation—a foundation that Euclid began in Book I with 23 definitions (such as “a point is that which has no part” and “a line is a length without breadth”), five unproved assumptions that Euclid called postulates (now known as axioms (axiom)), and five further unproved assumptions that he called common notions. (See the table (Euclid's axioms and common notions) of Euclid's 10 initial assumptions.) Book I then proves elementary theorems about triangles and parallelograms and ends with the Pythagorean theorem. (For Euclid's proof of the theorem, see the sidebar: Euclid's Windmill Proof.)The subject of Book II has been called geometric algebra because it states algebraic identities as theorems about equivalent geometric figures. Book II contains a construction of “the section,” the division of a line into two parts such that the ratio of the larger to the smaller segment is equal to the ratio of the original line to the larger segment. (This division was renamed the golden section in the Renaissance after artists and architects rediscovered its pleasing proportions.) Book II also generalizes the Pythagorean theorem to arbitrary triangles, a result that is equivalent to the law of cosines (see plane trigonometry (trigonometry)). Book III deals with properties of circles and Book IV with the construction of regular polygons, in particular the pentagon.Book V shifts from plane geometry to expound a general theory of ratios and proportions that is attributed by Proclus (along with Book XII) to Eudoxus of Cnidus (c. 390–350 BC). While Book V can be read independently of the rest of the Elements, its solution to the problem of (irrational numbers) is essential to later books. In addition, it formed the foundation for a geometric theory of numbers until an analytic theory developed in the late 19th century. Book VI applies this theory of ratios to plane geometry, mainly triangles and parallelograms, culminating in the “application of areas,” a procedure for solving quadratic problems by geometric means.Books VII–IX contain elements of number theory, where number (arithmos) means positive integers greater than 1. Beginning with 22 new definitions—such as unity, even, odd, and prime—these books develop various properties of the positive integers. For instance, Book VII describes a method, antanaresis (now known as the Euclidean algorithm), for finding the greatest common divisor of two or more numbers; Book VIII examines numbers in continued proportions, now known as geometric sequences (such as ax, ax^{2}, ax^{3}, ax^{4}…); and Book IX proves that there are an infinite number of primes.According to Proclus, Books X and XIII incorporate the work of the Pythagorean Theaetetus (c. 417–369 BC). Book X, which comprises roughly onefourth of the Elements, seems disproportionate to the importance of its classification of incommensurable lines and areas (although study of this book would inspire Johannes Kepler (Kepler, Johannes) [1571–1630] in his search for a cosmological model).Books XI–XIII examine threedimensional figures, in Greek stereometria. Book XI concerns the intersections of planes, lines, and parallelepipeds (solids with parallel parallelograms as opposite faces). Book XII applies Eudoxus' method of exhaustion (exhaustion, method of) to prove that the areas of circles are to one another as the squares of their diameters and that the volumes of spheres are to one another as the cubes of their diameters. Book XIII culminates with the construction of the five regular Platonic solids (Platonic solid) (pyramid, cube, octahedron, dodecahedron, icosahedron) in a given sphere.The unevenness of the several books and the varied mathematical levels may give the impression that Euclid was but an editor of treatises written by other mathematicians. To some extent this is certainly true, although it is probably impossible to figure out which parts are his own and which were adaptations from his predecessors. Euclid's contemporaries considered his work final and authoritative; if more was to be said, it had to be as commentaries to the Elements.Renditions of the ElementsIn ancient times, commentaries were written by Hero of Alexandria (Heron of Alexandria) (flourished c. AD 62), Pappus of Alexandria (flourished c. AD 320), Proclus, and Simplicius Of Cilicia (flourished c. AD 530). The father of Hypatia, Theon of Alexandria (c. AD 335–405), edited the Elements with textual changes and some additions; his version quickly drove other editions out of existence, and it remained the Greek source for all subsequent Arabic and Latin translations until 1808, when an earlier edition was discovered in the Vatican.The immense impact of the Elements on Islamic mathematics is visible through the many translations into Arabic from the 9th century forward, three of which must be mentioned: two by alḤajjāj ibn Yūsuf ibn Maṭar, first for the Abbāssid caliph Hārūn alRashīd (Hārūn arRashīd) (ruled 786–809) and again for the caliph alMaʾmūn (Maʾmūn, al) (ruled 813–833); a third by Ḥunayn ibn Isḥāq (808–873) was revised by Thābit ibn Qurrah (Thābit ibn Qurra) (c. 836–901) and again by Naṣīr alDīn alṬūsī (Ṭūsī, Naṣīr alDīn al) (1201–74). Euclid first became known in Europe through Latin translations of these versions.The first extant Latin translation of the Elements was made about 1120 by Adelard Of Bath, who obtained a copy of an Arabic version in Spain, where he traveled while disguised as a Muslim student. Adelard also composed an abridged version and an edition with commentary, thus starting a Euclidean tradition of the greatest importance until the Renaissance unearthed Greek manuscripts. Incontestably the best Latin translation from Arabic was made by Gerard of Cremona (c. 1114–87) from the IsḥāqThābit versions.The first direct translation from the Greek without an Arabic intermediary was made by Bartolomeo Zamberti and published in Vienna in Latin in 1505; and the editio princeps of the Greek text was published in Basel in 1533 by Simon Grynaeus. The first English translation of the Elements was by Sir Henry Billingsley in 1570. The impact of this activity on European mathematics cannot be exaggerated; the ideas and methods of Kepler, Pierre de Fermat (Fermat, Pierre de) (1601–65), René Descartes (Descartes, René) (1596–1650), and Isaac Newton (Newton, Sir Isaac) (1642 [Old Style]–1727) were deeply rooted in, and inconceivable without, Euclid's Elements.Other writingsThe Euclidean corpus falls into two groups: elementary geometry and general mathematics. Although many of Euclid's writings were translated into Arabic in medieval times, works from both groups have vanished. Extant in the first group is the Data (from the first Greek word in the book, dedomena [“given”]), a disparate collection of 94 advanced geometric propositions that all take the following form: given some item or property, then other items or properties are also “given”—that is, they can be determined. Some of the propositions can be viewed as geometry exercises to determine if a figure is constructible by Euclidean means. On Divisions (of figures)—restored and edited in 1915 from extant Arabic and Latin versions—deals with problems of dividing a given figure by one or more straight lines into various ratios to one another or to other given areas.Four lost works in geometry are described in Greek sources and attributed to Euclid. The purpose of the Pseudaria (“Fallacies”), says Proclus, was to distinguish and to warn beginners against different types of fallacies to which they might be susceptible in geometrical reasoning. According to Pappus, the Porisms (“Corollaries”), in three books, contained 171 propositions. Michel Chasles (Chasles, Michel) (1793–1880) conjectured that the work contained propositions belonging to the modern theory of transversals and to projective geometry. Like the fate of earlier “Elements,” Euclid's Conics, in four books, was supplanted by a more thorough book on the conic sections (conic section) with the same title written by Apollonius of Perga (c. 262–190 BC). Pappus also mentioned the Surfaceloci (in two books), whose subject can only be inferred from the title.Among Euclid's extant works are the Optics, the first Greek treatise on perspective, and the Phaenomena, an introduction to mathematical astronomy. Those works are part of a corpus known as “the Little Astronomy” that also includes the Moving Sphere by Autolycus of Pitane.Two treatises on music, the “Division of the Scale” (a basically Pythagorean theory of music (Pythagoreanism)) and the “Introduction to Harmony,” were once mistakenly thought to be from The Elements of Music, a lost work attributed by Proclus to Euclid.AssessmentAlmost from the time of its writing, the Elements exerted a continuous and major influence on human affairs. It was the primary source of geometric reasoning, theorems, and methods at least until the advent of nonEuclidean geometry in the 19th century. It is sometimes said that, other than the Bible, the Elements is the most translated, published, and studied of all the books produced in the Western world. Euclid may not have been a firstclass mathematician, but he set a standard for deductive reasoning and geometric instruction that persisted, practically unchanged, for more than 2,000 years.Bartel Leendert van der Waerden Christian Marinus TaisbakMajor WorksEuclid's extant works are collected in Euclidis Opera Omnia, ed. by J.L. Heiberg and H. Menge, 9 vol. (1883–1916), containing the Elementa, Libri I–XIII, Elementorum, Data, Optica, and Phaenomena.The standard English translation of the Elements is T.L. Heath, The Thirteen Books of Euclid's Elements, 3 vol., (1908; 2nd ed., rev. with additions, 1926). A restoration of Euclid's On Divisions is Raymond Clare Archibald, Euclid's Book on Divisions of Figures (1915). Euclid's contributions to astronomy are accessible in a recent English translation and commentary by J.L. Berggren and R.S.D. Thomas, Euclid's Phaenomena (1996).Christian Marinus TaisbakAdditional ReadingGeorge Sarton, Introduction to the History of Science, 3 vol. in 5 (1927–48), vol. 1, pp. 153–156, contains an extensive bibliography up to the 1920s. Thomas L. Heath, A History of Greek Mathematics (1921, reprinted 1993), vol. 1, pp. 354–446, presents an authoritative survey of Euclid's works; it can be supplemented by Victor J. Katz, A History of Mathematics: An Introduction, 2nd ed. (1998), pp. 58–101, whose bibliography refers to most recent treatments of Euclid's works. Information on Euclid and Platonism is contained in Glenn R. Morrow (trans.), Proclus: A Commentary on the First Book of Euclid's Elements (1970, reprinted 1992). A recent accessible contribution to the literature is Benno Artmann, Euclid: The Creation of Mathematics (1999).Christian Marinus Taisbakcity, Cuyahoga county, northeastern Ohio, U.S., on Lake Erie, just northeast of Cleveland. The original township area was settled in 1797 and was named for the famous Greek mathematician by the surveyors who arrived with Moses Cleaveland, an agent of the Connecticut Land Company. It remained largely rural, noted chiefly for grapes, until after 1940, when there was rapid industrial and urban growth. Manufactures now include airplane parts, assemblyline equipment, motors, metal fasteners, electrical and welding equipment, and earthmovers. Inc. village, 1903; city, 1930. Pop. (2000) 52,717; (2005 est.) 49,619.* * *
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